1. Field of the Invention
The present invention relates to a power storage apparatus connected between a generator and an electrical load and, in particular, the invention pertains to a power storage apparatus provided with a capacitor module including a plurality of capacitors.
2. Description of the Background Art
Motor vehicles featuring an idle stop and start function which stops an engine when a vehicle is stopped and an electric power steering system for reducing an engine load are used in recent years from a viewpoint of environmental considerations and an improvement in fuel economy. Also, systems like a hybrid system capable of positively providing an additional driving force to an engine and a regenerative braking system aimed at restoring kinetic braking energy produced when the vehicle is braked in the form of electrical energy currently receive much attention. As will be recognized from the above, there is a growing tendency today that the motor vehicles are required to make use of a larger amount of electric power. To cope with this tendency, recently proposed systems include large-capacitance capacitors, such as electric double-layer capacitors, that can be quickly charged and discharged.
A conventional power storage apparatus in which a plurality of capacitors are series/parallel-connected are provided with connection changing means for changing series/parallel connections of the capacitors. The connection changing means reconfigures the series/parallel-connected capacitors in such a way as to increase the number of series-connected capacitors during quick charge operation and to increase the number of parallel-connected capacitors during normal charge operation (refer to Japanese Laid-open Patent Application No. 1991-252528, for example).
A power storage apparatus connected between a generator and an electrical load starts up the generator by applying a voltage fed from the power storage apparatus to the generator at startup thereof. If the voltage of the power storage apparatus is low, however, it is necessary to produce a power source for starting up the generator by charging capacitors of the power storage apparatus. In this case, it is required to quickly charge the capacitors of the power storage apparatus in order to start up the generator. Although it would be possible for the aforementioned conventional power storage apparatus to quickly charge the capacitors upon increasing the number of the series-connected capacitors, there has been a problem that the capacitors would deteriorate to a large extent because all of the capacitors should be quickly charged and discharged.